The invention relates to a cooling device for electrical circuit configurations.
Electrical and electronic structural elements heat up during operation due to the occurring power dissipation. Heating therein as a rule is greater the higher the converted electrical power. To eliminate the heat from the particular structural element, different methods are possible. With electronic amplifiers in which power transistors become strongly heated, cooling fins and slots or Peltier cooling elements are used. These methods of cooling rest in principle on the use of air as means of heat dissipation. For fast and intensive cooling, however, air is often not sufficient. In these cases use is made of the known water cooling which is applied for example with most Otto engines.
The cooling of passive electrical structural elements such as coils and capacitors presents a special problem since these elements generate magnetic or electrical fields during operation which can act like interference fields. Such coils and capacitors are employed, for example, in matching circuits for plasma paths wherein these matching circuits are disposed between a high frequency generator and the plasma path (cf. DE-OS 36 38 880; U.S. Pat. No. 4,207,137; J. Electrochem. Soc. Solid State Science, Vol. 114, No. 5, 1967, pages 505 to 508; J. Vac. Sci. Technol. B 5 (3), May/June 1987, page 647). The power converted in these coils and capacitors often amounts to a few hundred kilowatts or more so that coils and capacitors heat up strongly and can potentially be destroyed.
To cool for example the coils in the high frequency power range the coils are implemented as cylindrical coils which are wound from a tube. For cooling purposes a fluid is conducted through the tube.
Since at least one terminal of the coil has a potential relative to ground, the cooling fluid flowing in and out at this place is likewise at the potential. As a rule water is used as cooling fluid which has a greater or lesser degree of conductivity. Hereby a filled cooling hose connected to the coil represents an effective resistance relative to ground. This resistance must be as large as possible so that the degree of efficiency of the circuit is not significantly impaired and thermal damages to the cooling water hose are avoided. To this end, as feed lines carrying cooling water to the high-voltage connections one to two meters of plastic or Teflon hose are customarily used. This hose is rolled up and secured within the HF shielding where it functions as a degradation path. However, since water also represents a dielectric with losses, the HF fields couple into the cooling water and thereby convert electrical energy into heat energy; the water thus acts as an absorber. Therewith two contradictory requirements are presented: water hoses of maximum length for high-ohmic loading of the electrical connection, and a minimum amount of water because of the absorbing effect on the electromagnetic fields. These two demands are not at all or hardly ever consistent with conventional methods.
The invention is therefore based on the task of effectively cooling electrical structural elements and to achieve simultaneously a high-ohmic load of the electrical connection without allowing large electrical losses to occur.